COK-5 is a molecular sieve zeolite characterized by very thin crystals from about 6 to 20 nm in thickness and a distinctive X-ray diffraction pattern which distinguishes it from other known crystalline materials. COK-5 is a highly versatile catalyst useful in a variety of organic conversion reactions.
An example of thin crystal COK-5 and a method of preparation thereof is disclosed in WO 02/46099-A1, the disclosure of which is incorporated by reference herein in its entirety. WO 02/46099-A1 discloses synthesizing COK-5 with N,N,N,N′,N′,N′-hexaethylpentane diammonium dibromide (HEPDD) as the structure directing agent:(C2H5)3N+C5H10N+(C2H5)32Br−.The synthesis further involves a hydrothermal treatment step, which is carried out under conventional zeolite synthesis conditions, and can extend for as long as 7 to 10 days (see WO 02/46099-A1, Examples 1 and 2).
Thus far, HEPDD cations have been identified as the only organic compound known to direct the synthesis of COK-5. Limited by a single identified structure directing agent, the synthesis of COK-5 is a complex process requiring up to 10 days of heating to obtain a final product, as taught by WO 02/46099-A1. Extensive, prolonged heating and the absence of alternative structure directing agents (which could also expand the compositional ranges of the zeolite) lead to various difficulties and increased costs in the production of COK-5, as well as in catalyst manufacture involving COK-5 zeolitic materials.
Therefore, while HEPDD cations can be used as a structure directing agent for the synthesis of COK-5, a need remains for improved structure directing agents, capable of being used in a more simplified synthesis process.
According to the present invention, using one or more of 1,4-bis(N-propylpyrrolidinium)butane dications, 1,4-bis(N-butylpyrrolidinium)butane dications and 1,5-bis(N-propylpyrrolidinium)pentane dications as a structure directing agent, it has now been found that COK-5 can be synthesized by simpler processes and in shorter heating periods than was previously possible using HEPDD as the structure directing agent. Using these new directing agents, COK-5 can be made across a wide range of Si/A1 and Si/B atomic ratios under typical OH/SiO2 molar ratios in sodium, potassium, or lithium-containing gels. In addition, it is possible to produce COK-5 with extremely small crystal size resulting in a material having a unique powder X-ray diffraction (XRD) pattern.